Fixed- and variable-frequency sliding mode controller–maximum power point tracking converter for two-stage grid-integrated photovoltaic system employing nonlinear loads with power quality improvement features

Ravichandran Chinnappan,Premalatha Logamani,Rengaraj Ramasubbu

doi:10.1177/0020294019830120

Abstract

This article presents a reliable and efficient photovoltaic sliding mode voltage-controlled maximum power point tracking DC-DC converter–active power filter integration system to supply real power to grid. This integrated active power filter system performs power quality enhancement features to compensate current harmonics to make distortion-free grid supply current and reactive power employing nonlinear loads. The proposed proportional–integral–derivative–based sliding mode controller is designed with fixed-frequency pulse-width modulation based on equivalent control approach. The main objective of this paper is to design a photovoltaic system with a new sliding surface to force the photovoltaic voltage to follow the reference maximum power point voltage with the alleviation of slow transient response and disadvantages of chattering effects of variable-frequency hysteresis modulation sliding mode controller–maximum power point tracking. The perturbations caused by the uncertainties in climatic conditions and converter output bulk oscillations during grid integration are also mitigated. The features of the proposed photovoltaic–active power filter integration system are confirmed at different operating conditions through PSIM simulation software, and its performance is also compared with a conventional variable-frequency sliding mode-controlled maximum power point tracking. The obtained simulation and experimental results give good dynamic response under various operating conditions of environmental and local load conditions.

Highlights

Sliding mode controllers (SMCs), is a better candidate than conventional linear controllers for mitigating such low-frequency oscillations and load perturbations due to their excellent characteristics of stability, simpler implementation and robustness against parameters which are common in PV system.[4,12,13]
This paper proposes a design procedure of PID-based sliding mode (SM) voltage controller for PV-maximum power point tracking (MPPT) application
The main contribution of this paper is to provide the effective integration of PV energy source into the distribution grid with power quality features that can be done by constant-frequency sliding mode controllers (SMCs)-MPPT high stepup DC-DC converter[6,5,18,19] connected with gridinterfacing inverter

Summary

Introduction

This is mainly due to PV voltage oscillations caused by the second harmonic frequency of the grid[7] and nonlinear characteristics of PV cells depending on irradiance and temperature.[8] Among the various solution methods proposed in gridintegrated PV system to mitigate such voltage oscillations, the most preferable and the first alternative is a linear proportional–integral (PI) + pulse-width modulation (PWM), proportional–integral–derivative (PID) + PWM or peak current mode + PWM controller These controllers ensure stability with the ability to track the PV voltage reference generated by the MPPT algorithm under uncertainties in load perturbations and climatic conditions.[7,9,10] the main problem associated with these controllers is loss of stability due to low-frequency sinusoidal voltage perturbations imposed by the grid in the DC bus. To ensure stability of a voltage-oriented MPPT algorithm with fast settling time, alleviating high chattering magnitude and mitigating low-frequency oscillations of the PV voltage especially in grid-connected environment, the necessity of constant frequency operation of SMC-MPPT converter is an important one in this concern.[14,15,16]

Objectives

Results

Conclusion